The present invention relates to an improved art of rotary lawn mowers.
Rotary lawn mowers cut grass by rotating cutting blades housed in downward-opening housings along the grass. This kind of rotary lawn mowers include (1) lawn mowers of a type for use in a so-called bagging mode, which receive grass cut by cutting blades in grass receptacles such as bags and (2) lawn mowers of a type for use in a so-called mulching mode, which cut grass cut by cutting blades more finely within housings to discharge it downward of the housings. The bagging-mode lawn mowers can remove all cut grass (grass clippings), providing a good finished quality of grass cutting, and are thus commonly used in golf courses or the like. The mulching-mode lawn mowers can eliminate the need for the work of xe2x80x9cdumping grass clippingsxe2x80x9d by returning grass clippings to the lawns, and are thus commonly used in parks or the like.
It is, however, inconvenient to selectively use the two types of lawn mowers, depending on the purpose. In recent years, an art of enabling a single lawn mower to operate both in a bagging mode and in a mulching mode has been developed. This kind of lawn mower is disclosed, for example, in Japanese Patent Laid-Open Publication No. SHO-64-3441 entitled xe2x80x9cRotary Lawn Mower.xe2x80x9d
The conventional lawn mower has a grass discharge chute mounted on a top plate of a housing and a grass discharge bag attached to the grass discharge chute so as to receive grass cut by a cutting blade in the grass discharge bag (bagging mode). The lawn mower alternatively has a cover plate mounted on the top plate of the housing to discharge grass cut by the cutting blade downward of the housing (mulching mode).
It is preferable for some lawns to be able to return some amount of grass clippings to the ground and hold the rest in the grass discharge bag. Returning part of grass clippings to fill in intrarow spacings, for example, provides good appearance and also compost to the lawns.
The conventional lawn mower, however, only switch the cover plate or the grass discharge chute to the other to put all grass clippings in the grass discharge bag or return all grass clippings to the ground, and is not applicable to an intermediate use. Further, it is required to manually change the parts to switch between the bagging mode and the mulching mode, involving troublesome changing work.
To solve the problem, it would be possible to provide an opening and closing valve at an inlet of the grass discharge bag to appropriately switch the opening and closing valve. However, only the provision of the opening and closing valve does not enable efficiently returning part of grass clippings to the ground while receiving the rest in the grass discharge bag.
Thus desired is a lawn mower which can appropriately switch between a bagging mode, a mulching mode and an intermediate mode by simple operation.
According to the present invention, there is provided a lawn mower which comprises: a power source with an output shaft extending downward; a housing provided below the power source, opening downward; a cutting blade housed in the housing and attached to the output shaft; a grass discharge passage extending rearward from the housing; a grass receptacle removably mounted to a receptacle mounted portion provided at the grass discharge passage, for receiving grass cut by the cutting blade through the grass discharge passage; and a shutter provided at a passage opening of the grass discharge passage facing the housing; wherein, the shutter is configured to be rotatable about the axis of the output shaft so as to adjust the degree of opening of the passage opening.
Since the shutter is provided at the passage opening facing the housing, of the grass discharge passage extending rearward from the downward-opening housing, and the shutter is configured to be rotatable about the axis of the output shaft of the power source, the degree of opening of the passage opening can be desirably adjusted with the shutter. Only the simple control of the shutter opening allows appropriate switching between a bagging mode in which the shutter is fully opened to receive grass clippings in the grass receptacle, a mulching mode in which the shutter is fully closed to discharge grass clippings downward of the housing, and an intermediate mode between the bagging mode and the mulching mode, in which the shutter is opened to a desired degree. It is needless to change the parts every time the mode is switched.
Further, opening the shutter to a desired degree allows minute and preferable setting of the form of discharge of grass clippings, according to lawn conditions, required finished quality, or preference. Furthermore, switching to the intermediate mode allows the reduction of the discharged flow amount of grass clippings discharged from the housing to the grass receptacle. This results in a lengthened time of accumulation of grass clippings in the grass receptacle, reducing the frequency of replacement of the grass receptacle.
The housing preferably has a scroll portion for allowing grass cut by the cutting blade to swirl within the housing while guiding it to the grass discharge passage. A guide is preferably provided along the scroll portion beneath a top plate of the housing. A rear guide end of the guide is preferably opposed to the passage opening. The rear guide end is preferably placed higher in level than the bottom of the passage opening.
Lawn mowers for use in the bagging mode generally cause grass cut by cutting blades to swirl within housings while guiding it to grass discharge passages. The shape of the bagging-mode housings is thus generally spiral.
Lawn mowers for use in the mulching mode cut grass cut by cutting blades more finely by the cutting blades within housings. The shape of the mulching-mode housings is thus generally uniform in cross-sectional shape.
The shape of the housings for use in the bagging mode is thus different from the shape of the housings for use in the mulching mode.
The lawn mower of the present invention uses the single housing to operate in the bagging mode, mulching mode and intermediate mode. The present invention provides, for efficient bagging-mode operations, in the housing the scroll portion for allowing grass clippings to swirl within the housing while directing them to the grass discharge passage. Further, for efficient mulching-mode operations, the guide is placed along the scroll portion, being provided beneath the top plate of the housing, and the rear guide end of the guide is opposed to the passage opening.
When the shutter is opened, the scroll portion and the guide allow grass clippings to swirl while smoothly guiding them to the passage opening. When the shutter is closed, the guide guides grass clippings swirling in the scroll portion for smooth flow along the closed shutter. The same applies to the intermediate mode. With the single housing, operations in the bagging mode, mulching mode and intermediate mode can thus be more efficiently performed.
In the present invention, the height of the rear guide end of the guide for directing grass clippings toward the grass discharge passage is set greater than that of the bottom of the passage opening. Thus in the intermediate mode, grass clippings swirling along the guide can be easily taken into the grass discharge passage. As a result, a required amount of grass clippings can be securely received in the grass receptacle through the grass discharge passage. Thus in the intermediate mode, the ratio between the amount of glass clippings to be held in the grass receptacle and the amount of grass clippings to be discharged downward of the housing can be relatively precisely set. The workability in the intermediate mode can be further improved.
The rear guide end of the guide is preferably formed in a wave shape.
When the cutting blade is rotated, an air flow is generally produced along the guide below the guide. This flow tends to become a vortex flow at the rear guide end. When the vortex flow is excessive, grass clippings are likely to be drawn into the vortex flow. As a result, in the bagging mode or the intermediate mode, the grass clippings have difficulty in flowing into the passage opening.
In the present invention, as described above, the rear guide end of the guide has a wave shape. Thus air flows at depressions in the wave shape interfere with air flows at projections to reduce the generation of vortex flows, resulting in a straightened air flow flowing into the passage opening. As a result, in the bagging mode or the intermediate mode, grass clippings easily flow into the passage opening. Grass clippings are thus allowed to smoothly flow into the grass receptacle through the grass discharge passage to be more securely received.